The present invention relates to a synchronizer ring, and more particularly, to a type thereof having excellent friction characteristics and sufficient anti-abrasion and endurance characteristics, and provided with stabilized high quality.
Synchronizer rings have been conventionally used in synchronized gear-meshing type transmissions or speed changers. The synchronizer ring 1 shown in FIG. 1 is a friction ring for selectively synchronously sliding with and separating from a rotating opposing member, that is, a taper cone. The synchronizer ring 1 performs the essential operation of matching the circumferential speeds of rotating gears to avoid clashing therebetween when meshing.
As is well known, a conventional synchronizer ring 1, generally formed from brass (Cu--Zn alloy), is cylindrical with an outer surface provided with an outer rim portion 105 and a plurality of teeth 100, and an inner surface 101 for contacting the cone. The plurality of teeth 100 are provided at a predetermined interval to the extreme outer circumference of a synchronizer ring. The teeth 100 are for engaging with a different opposing member such as a toothed ring (not shown). A key groove 104 for engaging a synchronizer key (not shown) is provided to the outer rim portion 105. To the inner surface 101 of the synchronizer ring are provided a plurality of annular grooves 102 for applying friction force. Further, linear grooves 103 are provided, as necessary, orthogonally to the annular grooves 102 for allowing movement of lubricating oil.
Conventional synchronizer rings 1 formed with the above-described structure, must have in general high mechanical strength and high precision. Increases in transmission quality and performance in recent years have increased their reliability. However, in addition to reliability, transmissions are required to provide a luxurious or sporty feel when driving the car. To provide these attributes, the inner surface 101 of the synchronizer ring 1 must have excellent friction and anti-abrasion characteristics. This has increased requirements for friction and anti-abrasion characteristics of the inner surface 101 of synchronizer rings.
Various proposals have been made in an attempt to improve friction characteristic and anti-abrasion characteristic or wear resistance at the inner surfaces of the synchronizer rings. In one example, as described in Japanese Patent Publication (Kokoku) No. SHO-46-15043, a uniform mixture of metal, ceramic, and an oxide are sprayed and fuse-bonded onto the inner surface of the synchronizer ring. Also West German Patent No. 3705661 describes a method for producing a friction ring, the method being applicable during production of the synchronizer ring. In this method, a friction lining, formed from, for example, a sintered powder containing 80% by weight powdered metal material and 20% by weight powdered non-metal material, is flame sprayed onto the inner surface.
However, conventional synchronizer rings obtained by spraying and fuse-bonding a uniformly mixed mixture of metal, ceramic, and oxide onto the inner surface of the synchronizer ring or by flame spraying a friction liner, formed from, for example, a sintered powder containing 80% by weight powdered metal material and 20% by weight powdered non-metal material, onto the inner surface, do not provide friction or anti-abrasion characteristics sufficient to meet increasing consumer demands. Also, the synchronizer rings formed with these methods may lack sufficient strength when metal components are not evenly distributed. Further, quality may become insufficient due to local variation of compositions in the sprayed layer. Frequently, particles incompletely fused in the flame, or which scatter or bounce off during spraying, become trapped in the surface layer of the sprayed film. Because these particles have been known to form excessively rough areas on the surface, the friction characteristic can easily change over a period of time. When these particles become separated from the surface, they have been known to abrade various parts in the transmission. On the other hand, attempts have been made to reduce the excessively rough areas by grinding or machining the surface of the sprayed-on film, but grinding and machining increases costs and wastes materials, affecting the yield.